The French shot-stopper has been plagued by inconsistent performances of late, with his mistakes seeing the Whites drop to 17th spot.
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And in what is a major call, Meslier has been benched by Allardyce, with Joel Robles replacing him in the starting XI for Saturday's 3pm kick-off - which is being broadcast on TV.
It is the ex-Everton and Wigan star's first top-flight appearance for Leeds since he joined last summer.
Meslier has been a regular starter since joining Leeds on an initial loan deal in 2019, with the 23-year-old featuring in every Premier League game last campaigns.
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In his last three seasons, the ex-Lorient man has missed just three league matches for the Yorkshire outfit.
Allardyce alluded in his pre-match press conference that the Manchester United target wasn't guaranteed of a starting spot after shipping in 18 goals in his last five games.
Commenting on the goalkeeping situation being his most challenging issue, he said: "I don't ever see a problem in training because there's no real pressure there like there is in a game.
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"There's the goalkeeper coach working with [Meslier], there's nothing you can see to suggest or say anything other than you look at him and like all the keepers do together, he goes through the routine.
"There are a bit daft, a bit mad aren't they, because they love doing what they do.
"If you did that for an outfield player they'd get really bored but goalkeepers love it and they're a right good pack together.
"They're like a little family of their own and that will help him hopefully, but that for me lies to be probably the biggest decision I have to make today."
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Like Leeds, City have also made changes to their team with Pep Guardiola having one eye on Tuesday's Champions League semi-final match against Real Madrid.
The Citizens have made seven changes, with Jack Grealish, Kyle Walker, John Stones, Ruben Dias, Rodri and Bernardo Silva coming out, while Ederson has replaced Stefan Ortega between the sticks.
City had been due to host Leeds at the Etihad on Sunday, but the fixture was moved due to their involvement in the European Cup.
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And despite it being a 3pm kick-off, the game is being shown on TV as the 12:30pm slot wasn't an option due to King Charles III's coronation.
Meanwhile the 5:30pm slot wasn't available due to Liverpool welcoming Brentford to Anfield.
Originally selected for broadcast by Sky Sports, and after consultation with stakeholders, it was agreed that City's clash against Leeds could be shown live and break the 3pm blackout.
Man City team: Ederson, Ake, Akanji, Gundogan, Laporte, Lewis, De Bruyne, Alvarez, Mahrez, Foden, Haaland
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Leeds team: Robles, Ayling, Firpo, Forshaw, Wober, Roca, Harrison, Kristensen, McKennie, Gnonto, Bamford